TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2313 SUBJECT: XRF030723 (=H2777): An X-ray Flash Localized by the HETE WXM and DATE: 03/07/23 23:39:56 GMT FROM: George Ricker at MIT XRF030723 (=H2777): An X-ray Flash Localized by the HETE WXM and SXC G. Prigozhin, N. Butler, G. Crew, J. Doty, A. Dullighan, R. Vanderspek, J. Villasenor, T. Cline, J. G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Monnelly, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams; G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of the HETE Science Team; C. Barraud, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE FREGATE Team; T. Tamagawa, M. Suzuki, C. Graziani, Y. Shirasaki, T. Donaghy, M. Matsuoka, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, Y. Nakagawa, R. Satoh, Y. Urata, T. Yamazaki and Y. Yamamoto, on behalf of the HETE WXM Team; write: At 06:28:17.45 UTC (23297.45 s UT) on 23 July 2003, the HETE FREGATE, WXM, and SXC instruments detected an X-ray flash, designated XRF030723 (=H2777), located at high galactic latitude (b = 50 degrees). The burst triggered the WXM in the 2-25 keV energy band. The burst signal-to-noise was ~9. A GCN burst alert was issued 42s later, reporting a flight-derived WXM localization with a 30 arcmin radius (90% confidence). Ground analysis of the WXM data produced a localization that was reported in a GCN Notice at 09:47:25 UT. The WXM data provided a localization that can be expressed as a 90% confidence circle that is 9.4 arcminutes in radius and is centered at-- WXM-ground: RA= +21h 48m 52s, Dec= -27d 41' 16" (J2000) Ground analysis of the SXC data provided an initial localization that was disseminated as a GCN Notice at 13:38:19 UT. A refined SXC localization can be expressed as a 90% confidence circle that is 2 arcmin in radius and is centered at-- SXC-Ground: RA= +21h 49m 27.4s, Dec= -27d 42' 01" (J2000) The burst duration (t90) in the 7-30 keV band was ~23 s. A total of 1210 counts were detected by Fregate during that interval, corresponding to a fluence of ~2 x 10-7 ergs cm-2. The peak flux in a 1.2 s bin was >3 x 10-8 ergs cm-2 s-1 (ie >0.9 x Crab flux) in the same energy band. In the 30-400 keV band, the fluence was < 0.7 x 10-7 ergs cm-2, which is < 0.4 times the fluence in the 7-30 keV band; thus we conclude that H2777 is an X-ray flash. A light curve and finding chart for XRF030723 is provided at the following URL: http://space.mit.edu/HETE/Bursts/GRB030723 This message may be cited.